Heat vinegar, sugar, and oil in a microwavable container until hot, about 1 minute, stir into vegetables.
Bake in a 350 degree F. oven for about 1 1/2 hours, or until vegetables are softened and liquid has evaporated, stirring every 20 minutes. Remove pan from oven, discard bay leaf and stir in tomato paste.

STEP SEVEN:

Ladle into jars to within 1/2 inch of rim (headspace). Process in a boiling water bath, 15 minutes for half pint jars and 20 minutes for pint jars as directed.